The present invention relates to an apparatus and method for directly installing a shut-off valve in a flowing high pressure line and, more particularly, to such an apparatus and method for shutting off a flowing oil or gas well which is burning or out of control.
Apparatus and methods for handling oil well blow-outs and fires are well known in the art. One of the most common devices used to control a well is a blow-out preventer (BOP). A BOP or an array of BOPs are attached directly to the wellhead and operate to rapidly close an open well hole or the space between the casing and the drill pipe to prevent the escape of pressurized oil or gas. These devices work essentially as plugs and may be either insertable laterally into the casing (ram type BOP) or expandable radially to fill the casing (annular BOP). On a land well, the BOP is normally located at the ground surface and, in a subsea well, at the ocean floor.
Although blow-out preventers are effective in preventing blow-outs and ensuing fires, if the wellhead is damaged or if a fire occurs before the blow-out preventers operate to seal the well, BOPs may become largely ineffective. Once a well is out of control or on fire, resort must be made to other means to bring the well under control.
Various types of relatively unsophisticated, brute force methods are employed to control wild wells, including those which may be on fire. All of these methods operate essentially directly at the well head to attempt to cap and seal it off. Obviously, if the well is afire, greater difficulty and hazards must be faced.
U.S. Pat. No. 1,879,160 discloses a method and apparatus for shutting off a burning oil well by plugging the same from an access point below ground. The apparatus inserts a wedge-like plug laterally through a hole drilled in the production pipe (and outer casing, if present) to plug the pipe and seal off the flow. Mud and cement are then pumped into the pipe through the plug to seal off the well. This method and apparatus contemplates permanent sealing of the well and taking the same completely out of production.
The prior art also discloses various types of apparatus for installing a plug in a flowing high pressure pipeline which plug can be subsequently withdrawn and reseated as a fully operative valve. Each of these patents utilizes means to cut a hole through or cut a section out of the flowing pipeline while withstanding the pressure therein and then permanently placing the valve in position.
Nichols U.S. Pat. No. 3,699,996 shows an apparatus including a drilling and reaming tool to cut a cylindrical hole through the flowing pipeline using a powered rotational drive and an axial hydraulic ram. A valve seat and valve plug are mounted axially behind the drill and the seat automatically snaps into position upon completion of the drilling and the drill bit can be subsequently removed from the valve plug. This apparatus requires complex sealing and locking components and requires that the drill bit be removed from the seat/plug assembly before the valve is operable.
McKean U.S. Pat. No. 3,532,113 shows a combined cutting tool and gate valve which is used to cut a cylindrical hole laterally through the pipe and to close off the hole after cutting. The drill/gate may be subsequently withdrawn to open the valve, but the apparatus requires a complex variety of seals and packings to maintain a fluid tight valve.
Margrave U.S. Pat. No. 4,552,170 shows a somewhat similar device, except that the drill which cuts a cylindrical hole through the pipe is followed axially by a tubular elastomeric seal which is radially expandable to seal the hole in response to axial compression imposed on the elastomer when the advancing cutting tool engages a stop after passing through the pipe.
Hefetz U.S. Pat. No. 3,993,137 discloses an apparatus in which axially aligned and diametrically opposite drill and plug members are mounted in a confining saddle arrangement around an outer casing, and the interior pipe is immobilized by drills entering the pipe radially from different directions. A large drill is then used to cut through both the casing and the interior pipe, the drill is withdrawn, the drill access chamber closed, and a plug inserted from the diametrically opposite side to seal the casing. The plug is also capable of being withdrawn to function as a valve. Means are also disclosed for maintaining operational flow of the well while it is plugged by diverting the flow through the plug.
Stupak U.S. Pat. No. 4,516,598 also discloses a drill and a plug in axial alignment on diametrically opposite sides of the pipe. However, after a hole is drilled through the pipe, the drill is withdrawn, the mounting saddle rotated 180.degree., and the plug inserted into the hole to plug the pipe.
Harrison et al U.S. Pat. No. 4,108,194 shows a method and apparatus for providing a tapered pipeline seal in which a straight cylindrical hole is first drilled through the pipe and the cylindrical hole is then reamed to a taper adapted to receive a subsequently inserted tapered plug to seal the hole. However, no means are described for holding against pressure in a flowing pipe while drilling, reaming, or changing tools. The apparatus and method are only useful in plugging an empty pipeline.
Therefore, an apparatus and method which operates simply and effectively to seal off a flowing high pressure pipeline with a minimum of complex components would be most desirable. In particular, a device which utilizes the drilling and/or finishing tool as an integral part of the operating valve would be most desirable. Also, any such apparatus must be capable of accommodating the high stresses encountered in the rotary drilling members, particularly when tapping into a flowing, high pressure oil well pipe.